Plants are often grown in containers by the nursery industry so that the plants can be shipped directly to the market without the need for transplanting. Container grown plants produce numerous advantages to the nursery by reducing labor cost, as well as handling, packaging and other operating costs. In addition, growing plants in containers provides comparatively simplified weed control and enables controlled irrigation and fertilization. Because water only needs to be provided to the plant confined by the container, less water per acre is needed to promote rapid and efficient plant growth.
Growing plants in containers does, however, have several disadvantages. The soil mixture used for container grown plants usually has poor water retention so that watering must be regularly carried out to prevent the roots from becoming too dry. In addition, the containers are often placed above ground and in direct sunlight and wind which contribute to rapid water evaporation. The containers above ground are also subject to freezing temperatures which can damage the roots. Finally, winds will often blow the containers over thereby spilling the soil and damaging the plants.
To minimize these disadvantages associated with container grown plants, many nurseries anchor or bury the container in the ground. This reduces the risk of the roots freezing and the plant from blowing over in high winds. A significant disadvantage of buried containers is the difficulty of removing the container from the ground before the plants can be shipped. Moreover, the roots from the plant grow outward through the drain holes in the container into the surrounding soil. This increases the amount of effort required to remove the container from the ground and usually results in root damage to the plant. An example of this type of growing system is shown in U.S. Pat. No. 5,007,135. This growing system provides a sufficiently large opening in the container to encourage the roots to grow outwardly into the surrounding soil. The roots are then cut by a shovel or other tool to remove the container from the ground which inherently results in damage to the root system.
In recent years, many nurseries have used a below ground system where an empty container is buried in the ground and a growing container containing the plant is placed in the buried container. This system is often referred to in the industry as a pot-in-pot system. The system has several advantages over other growing systems. In particular, the pot-in-pot type system provides protection for the roots to resist freezing and from drying out in the sun. In addition, the buried container anchors the plant container and reduces the risk of the plants from blowing over in high winds.
As in other below ground growing systems, the roots from the growing container often grow outward from the drain holes into the below ground container. The below ground container is required to have drain holes to prevent excess water from remaining in the container which will otherwise cause the roots to rot and kill the plant. Often times the roots from the growing container will grow outward through the drain holes of the below ground container and into the surrounding soil. When this occurs, it is difficult to remove the growing container from the below ground container since the containers are now tangled with the root system. Often the growing container cannot be separated from the below ground container without removing both containers from the ground and cutting the roots. This disadvantage increases the labor costs and damages the root system of the plant.
Examples of various plant growing containers are disclosed in U.S. Pat. Nos. 4,106,235 to Smith, 5,279,070 to Shreckhise et al, 5,099,609 to Yamauchi and 1,665,124 to Wright and Italian Patent No. 681968 and French Patent No. 427,391. These patents disclose plant container systems having a plant container and a receptacle container for receiving the plant container and holding water for supplying water to the plant. U.S. Pat. Nos. 5,515,783 to Peng, 4,232,482 to Watt et al, 4,027,429 to Georgi and 1,533,342 to Schein disclose growing containers having a tray or other container below the plant container for collecting water. These containers do not provide a system for preventing the roots of the plant from becoming entangled with the other container.
Accordingly, there is a continuing need in the industry for improved plant growing system which overcomes the above disadvantages.